Effective bonding of glass to painted substrates is important in such industries as the automotive industry. For instance, windshields must be effectively bonded to an auto body in order to support the roof of the automobile in cases of crashes or rollovers. Typically, a urethane sealant is used to attach the glass surface to the painted surface. However, sometimes it is difficult to satisfactorily adhere urethane sealants directly to painted surfaces.
Consequently, in order to obtain acceptable levels of urethane adhesion to painted auto body surfaces, auto manufacturers often require an extra preliminary step of applying a primer coating to the painted surface before applying the adhesive. For example, U.S. Pat. No. 4,525,511, entitled "Method and Compositions for Improving Bonding to Painted Surfaces", describes such a primer and method for priming (incorporated herein by reference). Only through use of such a priming top coat can satisfactory adherence of the urethane sealant and joinder of paint-glass surfaces be achieved.
U.S. Pat. No. 4,857,366 (the '366 Patent), issued to Schumacher, entitled "Method for Obtaining Adhesion of Urethane Sealant to a Painted or Glass Surface", represents an advance in the art of glass-painted surface bonding, because the primer step was eliminated (incorporated herein by reference). The '366 Patent describes a method for treatment of a painted surface to achieve adhesion of a urethane sealant to the painted surface. The method described therein includes applying a solution of paratoluene sulfonic acid and a solvent selected from the group consisting of ketones, alcohols and aliphatic esters. However, the solvents described in the '366 Patent are relatively environmentally hazardous. Moreover, the solutions described in the '366 Patent often leave an unsightly acid residue on the treated surface, thereby adversely affecting the gloss of certain types of paint.
It would be an advance in the adhesives and sealants art to provide a method and composition for treating a painted surface which can efficiently improve adhesion between the urethane sealant and the painted surface. It would also be an advance in the art to provide a more environmentally friendly composition than the compositions described in the above prior art, and which does not leave an unsightly residue on the painted surface and does not adversely affect the gloss of the painted surface.